Treatment of hydrocarbon oils



Patented Aug. 10, 1937 UNITED STATES.

I 2,039,519 TREATMENT or nrnaocmon ons Walter A. Schulze, Bartlesville, Okla, assignor to Phillips Petroleum kla., a corporation of Delaware Company, lesville, 1

No Drawing. Application September 10, 1934, Serial No. 143.492

10 Claim.

This invention relates to the prevention of corrosion of metals, and refers more particularly to a new and improved treatment of hydrocarbon oils containing sulfur. It includes both the meth- 5 0d of treatment and the product obtained.

More specifically this invention relates to the treatment of hydrocarbon liquid fuels ranging from liquefied petroleum gases through kerosene to prevent or retard or inhibit the corrosive action of elementary sulfur on such metals as copper, bronze, etc.

Gasolines as commercially produced always contain more or less elementary sulfur result ing from the oxidation or decomposition of hydrogen sulfide and/or organic sulfur compounds during fractionation or other heat treatment of these products. Furthermore, during the doctor sweetening operation wherein free sulfur is added to the oil for the purpose of converting the lead mercaptides to lead sulfide and alkyl disulfides, some excess of free sulphur must be used in order that the breaking out operation can'be obtained in a reasonable amount of time. Therefore, regardless of how the oils are produced some- 5 free sulphur is practically certain to be present and such sulfur reacts readily with copper and its alloys when the said oils are in contact with such metals.

Similar problems or disadvantages are met with liquefied petroleum gases which is the name applied to a material similar to gasoline in physical properties but which consists largely of low boiling hydrocarbons such as propane and butane kept in the liquid state by the use of pressure.

If such liquefied gases are drawn off in the vapor form then free sulphur will be concentrated in the containers and over a periodof time the quantity may become quite large. It is common. practice in dispensing liquefied petroleum gases it) to use certain materials containing copper and its alloys, and such materials are particularly subject to corrosion by free sulphur. This corrosion and consequent weakening of the materials is especially dangerous where such elevated .45 pressures are necessary.

At the present time-it is necessary totreat the crude hydrocarbon products by very rigorous and expensive methods in order that the quantity of free sulphur present in the finished products $9 is suficiently low that the rate of corrosion will notbe exorbitant.

I have now discovered that by the addition of small amounts of certain compounds to the free sulphur containing hydrocarbon oils the cor-, $1 rosive action of the sulphur on such metals as" copper and its alloys is prevented or retarded or inhibited. The compounds which I include in this invention are those containing a hydroxyl and a carbonyl radical attached either to the same carbon atom 'or to its equivalent in a con- 5 jugated system. Polyhydroxy compounds and compounds containing nitrogen, e. g. the amino derivatives, are notintended to be included in this definition.

v CH=CH Para-hydroxy benzophcnone, 0H

. g v Y 011-011 wherein the carbonyl group and the hydroxyl group are attached to the 1,4 carbons respectively of. a conjugated system, is particularly outstanding in its effectiveness in preventing the action of free sulphur on copper. Other pompounds of similar structure are fluorescein and phenolphthalein.

isan example of a compound wherein the carbonyl group and the hydroxyl grqup attached to the same carbon atom have given good results in preventing sulphur corrosion. The lactic acid esters, e. g.-etl1yl and butyl, are examples of other compounds belonging in this classification which have been found to be quite effective.

According to this invention a small amount of one of the compounds mentioned, e. g. paiahydroxy benzophenone, is added to a hydrocarbon oil containing elementary sulphur. In general the preferred actual concentration of the compound may vary between the limits of 0.001 percent to 0.1 percent. Such quantities give good results but larger or smaller amounts of the inhibitor may beused without departing from the 'scope of this invention.

The amount of the compound needed to prevent corrosion of thecopper depends to some extent on the amount of free sulphur in the hydrocarbon solution. The percent of the compound'to be used in the oil depends, also, on theratio oi the surface area of the copper to the volume of the oil.

v It is to be understood'that the corrosion-preventing agent may be added either to a hydrocarbon oil already containing free sulfur or to an oil whichmay subsequently contain elementary sulfur as a-result oi the decomposition and/or 55 the oxidation of unstable sulfur compounds there- I have found that the various compounds are not equally effective and that much larger quantitles of certain of the compounds must be used if equivalent efi'ectiveness is to be obtained In general the results indicate that (1 those compounds mentioned above containing the hydroxyl attached to the para position in the benzene nucleus with the general formula 5 wherein represents either an alkyl or' an aryl group are more effective than the aliphatic compounds mentioned above and (2) the simple alkyl groups such as methyl and ethyl are considerably better than butyl and amyl. It is be- 0 lieved that the molecules containing the longer chains are less tightly held (absorbed) on the for several; hours. The duration of the heating period before appearance of discoloration on the copper strip is the measure of the corrosiveness of. the oil. Another test which is used is that of merely noting the'time during which no dis-- coloration appears on the: copperistrip immersed.

in a sulfur-bearing .naphtha solution at room temperature. a

The following examples will illustrate the usefulness ofmy process:

Example Ina-0.00086 percentelementary sulfur was added to a freshly distilled light naphtha. A copper strip immersed in a 60 =cc,.portion of this naphtha was quite badly corroded after standing 20 minutes at room temperature whereas a copper strip immersed in a similar portion of the naphtha to which was added 0.005 percent para-hydroxy-benzophenone showed no discoloration or corrosion at the end of 71 days.

Example 2.--'I'he'copper strip'immersed in a 50 cc. portion of naphtha containing 0.00086 percent elementary sulfur and 'a little parahydroxy-benzophenone showed no discoloration after standing 6 hours-at room temperature and heating three hours at F. wherea's'the copper strip in the untreated sample was badly corroded in. a short time at room temperature.

Example 3.The copper strip immersed ln'a- 50 cc. portion of naphtha containing 0.00086 percent elementary sulfur ahd-alittl n-butyld-l-malate showed no discoloration"olf corroslon' after standing 6'hours at room temperature, 4 hours at M0 F. and lfi'hours more at room temperature whereas'the copper strip in the untreated sample was badly corroded within a few minutes at room temperature.

In a similar test n-butyl lactate was found to be quite effective at room temperature butpsomewhat less effective than the corresponding malate at elevated temperatures j It is not de'siredto limit the invention to any specific concentration of the "treating fag'ents since use may be madejfof'hlgher .or lower concentrationslof any member s of th'eclasses of compounds inentionedherein. 'and as a result thereof longer or'shorter perlods of preventing,

retarding 'or inhibiting corrosion of copper and its alloys by elementary sulfur secured depending" upon the specific agent used, the concentration of the agent, the percentage of free sulfur in the material treated and the conditions under which the subsequent storage takes place.

Obviously these various. compounds differ greatly in their solubility in hydrocarbon oils. Some of them are practically insoluble while others are readily'soluble. Inasmuch as the desired solubility can usually be obtained by I the introduction of more oil soluble" or less oil soluble" groups into such compounds, it is to be understood that such maybe made without departing from the spirit'- and scope of this invention. Misoibillty agents such as butyl alcohol can sometimes be added with the more insoluble compounds to increase their solubility in the hydrocarbon oils.

1 claim:

l. The method of inhibiting the corrosion of copper and its alloys by hydrocarbon liquid fuels ranging from, liquefied petroleum gases through kerosene, said liquid fuels containing sumcient elementary sulfur so that they tend normally to corrode copper and its alloys,. which comprises adding to the said liquid fuels 9. small amount of a compound of the structure ll-E0011 I wherein 13. represents a member selected 'fromthe group consisting of the alkyl and aryl groups.

2. The method of inhibiting the corrosion of copper and its alloys by hydrocarbon liquid fuels ranging from'liquefied petroleum gases through kerosene, said liquid fuels containing sufliclent elementary sulfur so that they tend normally to corrode copper and its alloys. which comprises adding to the said liquid fuels 9. small amount of para-hydroxy-benzophenone.

3, Predominantly hydrocarbon liquid fuels ranging from liquefied petroleum gases through kerosene containing sufiicient elementary sulfur to tend normally to corrode copper and itsalloys to which has been added as a corrosion inhibitor a small amount of a compound of the structure Reg-G an wherein R represents a member selected from the group consisting of the alkyl and aryl groups.

6. Motor fuel containing suflicient' elementary sulfur to tend normally to corrode copper and its alloys in contact with said fuel, to which has been added as a corrosion inhibitor a small amount of para-hydroiw-benzophenone.

7. The method of inhibiting the corrosion of :opper and its alloys by light hydrocarbon oils iubstantially free of unsaturated hydrocarbons Jut containing suificient elementary sulfur to :end normally to corrode copper and its alloys, which comprises adding to the said liquid fuels 2. small amount of a compound of the structure R-EOOH wherein R represents a member selected from the group consisting of the alkyl and aryl groups.

8. Light hydrocarbon oil substantially free of unsaturated hydrocarbons containing sufllclent sulfur so that they tend normally" to corrode copper and its alloys to which has been added as a corrosion inhibitor a small amount of parahydroxy-benzophenone.

9. Liquefied petroleum gas containing sufiicient elementary sulfurto tend normally to corrode copper and its alloys in contact with said fuel, to which has been added as a corrosion inhibitor a small amount of a compound of the structure wherein R represents a member selected from the group consisting of. the alkyl and aryl groups.

10. Liquefied petroleum gas containingsufficient elementary sulfur to tend normally to corrode copper and its alloys in contact with said fuel to which has been added as a corrosion inhibitor a small amount of para-hydroubenzophenone.

WALTER A. SCHULZE. 

